The strange tale of the antibiotic that kills fear

I heard about this the first time from Prof Isaac
Marks. He was talking about ways of making the treatment of extreme
fear of stuff -- or phobias -- more effective. He described how, using an
antibiotic, one could make a treatment session more effective. There are other meds that have been used
for one thing and then turned out to be helpful for another; so the idea isn't
as strange as it may seem. Aspirin is the best known example of this: used
first as a painkiller and then found to be also useful in reducing the risk of
strokes and heart attacks.

Made by bacteria to kill bacteria

The antibiotic in
question is called cycloserine and it was discovered by two microbiologists,
Roger Harned and Eleanore Kropp, in 1955. They found it when working with
bacteria called streptomyces orchidaceus, which make it. To this day drug
companies use these bacteria to produce it. Doctors used it to treat
tuberculosis and other infections. That was its only use for many
years.

Doctor, can this antibiotic change my
emotions?

Some people using this antibiotic experienced
side-effects affecting their emotional health, which led doctors to investigate
why this was happening. It turned out cycloserine affects the way a chemical
works in a particular area of the brain. This particular area is called the
amygdala.

Enter the amygdala

The amygdala is the size and shape of an almond and
-- among other things -- it is very important when forming memories of things
we become fearful of. Sometimes these fears are very useful and they make us
avoid harmful things. Sometimes this doesn't work so well and one can become
fearful of something that is really not that harmful. When researchers
discovered that some of the side-effects of cycloserine were because of its
effects on the amygdala the light bulb went off. They thought cycloserine might be able to
help get rid of those undesirable strong fears by making therapy more
effective.

OK, nice theory, but does it really
work?

Being a cautious lot, researchers from Emory
University began experimenting with rats in 2003. They started by making rats
severely fearful of a certain situation and then they gave them cycloserine
when helping them overcome their fear (yes, as strange as it sounds you can
treat rats for their phobias). They compared them with rats not taking the
cycloserine but going through the same treatment. Their results were that the
rats using cycloserine got better sooner.

Encouraged by their findings they went on to try
this on people suffering from acrophobia (fear of hights). They already knew
cycloserine was safe in people as it had been used as an antibiotic for 50
years. Their results were also very encouraging. It seemed that those using the
cycloserine in therapy improved much more than those not using it. You can
read
their paper here.

Other researchers have since shown the same effects
in other phobias and also with other conditions associated with anxiety and
stress. In 2008 a paper
by Melissa Norberg and her team looked at all the research done with
cycloserine up to that time and concluded that it is useful in therapy.
They found that it is best to use right before or after therapy, but not otherwise,
and that it was no good giving it too many times.

Odd but true

So, there you have it. My guess is that -- even
though cycloserine started off as an antibiotic -- it is now used probably more
often when treating phobias and other anxiety complaints. It is not without its
side-effects so sometimes we cannot use it. That is why people are looking for
new drugs that do similar things in the amygdala, but not cause so many
problems. If you have a phobia your doctor or therapist might talk to you about
it and, when she or he does, you won’t think it so strange.

If you have taken cycloserine I would like to hear
about it. Did it work? Did it cause any problems? Please leave a comment and
share your experience.